#include        <stdio.h>
#include        <stdlib.h>
#include        <unistd.h>
#include        <fcntl.h>

#define BUFFERSIZE      4096
#define COPYMODE        0644

void oops(char *, char *);

int main(int argc, char *argv[])
{
    int in_fd, out_fd, n_chars;
    char buf[BUFFERSIZE];
    if (argc != 3) {
        fprintf(stderr, "usage: %s source destination\n", *argv);
        exit(1);
    }

    if ((in_fd = open(argv[1], O_RDONLY)) == -1)
        oops("Cannot open ", argv[1]);

    if ((out_fd = creat(argv[2], COPYMODE)) == -1)
        oops("Cannot creat", argv[2]);

    while ((n_chars = read(in_fd, buf, BUFFERSIZE)) > 0)
        if (write(out_fd, buf, n_chars) != n_chars)
            oops("Write error to ", argv[2]);
    if (n_chars == -1)
        oops("Read error from ", argv[1]);


    if (close(in_fd) == -1 || close(out_fd) == -1)
        oops("Error closing files", "");
}

void oops(char *s1, char *s2)
{
    fprintf(stderr, "Error: %s ", s1);
    perror(s2);
    exit(1);
}
